Permanent magnet type loudspeakers



March 15, 1966 J. F. EICHLER PERMANENT MAGNET TYPE LQUDSPEAKERS Filed Jan. 31, 1962 INVENTOR JAMES F. EICHLER,

BY HIS ATTORNEY.

United States Patent 3,240,882 PERMANENT MAGNET TYPE LOUDSPEAKERS James F. Eichler, North Syracuse, N.Y., assignor to General Electric Company, a corporation of New York Filed Jan. 31, 1962, Ser. No. 170,144 3 Claims. (Cl. 179--115.5)

This invention relates to permanent magnet type loudspeakers, and more particularly to a removable type magnetic structure which is utilized therein.

In the manufacture of permanent magnet, moving coil type loudspeakers the magnetic structure which forms an air gap for the moving coil is fixedly mounted to the frame which carries the diaphragm and the moving coil. When the speakers are subjected to test, some are rejected and must be discarded without the opportunity of salvaging various portions thereof. If a removable construction would be provided which would permit the removal of the magnetic structure from the diaphragm housing then the cone, voice coil and spider assemblies of most speakers could be salvaged. Also, if the speaker was rejected because the air gap had become contaminated with metal chips or other foreign particles, the magnet and cup assembly could be cleaned and replaced making the salvage of the complete speaker assembly possible.

Accordingly, it is an object of this invention to provide an improved loudspeaker assembly which has a magnetic cup which is removable from the rest of the as sembly.

It is a further object of this invention to provide a new and improved two-piece magnetic cup structure which facilitates the production of loudspeakers of the moving coil permanent magnet type.

A further object of this invention is to provide a new and improved magnetic structure for permanent magnet type loudspeakers which not only facilitates the manufacture of such speakers but also reduces the cost thereof.

In carrying out this invention in one illustrative embodiment thereof, a composite magnetic unit for a permanent magnet type loudspeaker is provided including a two-element molded cup construction. One element consists of a cup of magnetic material having a mouth at an end thereof which is adapted to receive an annular element of molded magnetic material to form the two-element cup construction. A pole piece element is secured within the cup at a closed end and forms an annular magnetic air gap with a ortion of the annular element of magnetic material. The annular element of magnetic material is provided with projections which cooperate with slots located in a frame of the speaker for providing demountable means of securing the magnetic unit to the speaker assembly.

The invention, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIGURE 1 is a sectional view of the loudspeaker embodied in this. invention,

FIGURE 2 is a sectional view taken along lines 2-2 of FIGURE 1 showing the demountable construction of the magnetic unit employed in this invention, and

FIGURE 3 shows an enlarged, exploded view of the magnetic unit utilized in this invention.

Referring now to FIGURE 1, a loudspeaker is shown having a diaphragm housing frame 12 which contains a diaphragm 20. The larger end of the frame 12 supports the diaphragm 20 while the smaller end of the frame 12 terminates in a shoulder 14 having an aperture 15 with a perimeter including a slot segment 3,240,882 Patented Mar. 15, 1966 18. That portion of the frame defining the junction of the aperture forms a flange 16 thereon adapted to mount a composite magnetic unit 30.

The magnetic unit 30 is best illustrated in FIGURE 3. A molded cup element of magnetic material 32 is provided with an annular shoulder 34 and an annular ridge 36 at a mouth portion 35 thereof. The cup element includes a circular inner surface 37 best seen in FIGURE 1. An annular element 38 of molded magnetic material having a flange 40 thereon and projections 42 on the flange 40 provided. Element 38 includes a body portion 43 and is adapted to be mounted within the mouth portion 35 of the magnetic cup 32 with a surface of the flange 40 resting on the annular ridge 36. This mounting may be a press fit or other suitable means such as cementing. The body portion 43 thus provides an inner shoulder 45 for the cup which is best seen in FIGURE 1. A permanent magnetic pole piece element 44 is mounted by cementing or other suitable means at a closed end of cup 32 to form an annular air gap 25 between the upper end of the pole piece 44 and the shoulder 45 formed by the body portion 43 of annular element 38. The small end of the diaphragm 20 carries a voice coil form 24 having a voice coil 26 thereon which is positioned in the air gap 25. A flexible corrugated spider 22 is utilized to center the voice coil 26 in the air gap 25.

The demountable feature of the magnetic unit 30 is best shown in FIGURE 2. The flange 16 of the annular shoulder 14 of the frame 12 is provided with a plurality of slotted segments 18 along its periphery. Flange 16 is also bent inward in varying amounts in a spiral type configuration. The magnetic unit 30 is mounted on the diaphragm voice coil housing frame by inserting the projections 42 in the slots 18 and rotating the magnetic structure 30 to a position such as that shown in FIGURE 2. Rotation of the projections 42 bring the spiral shape flange 16 into contact with the annular shoulder 34 of the magnetic cup to provide a firm, yet demountable means for mounting the magnetic unit 30 to the frame 12 which carries the rest of the loudspeaker structure. The spiral shape of the flange 16 provides a locking action once the magnetic unit is rotated a given distance.

This demountable construction provides a means of salvaging the diaphragm, voice coil and spider assemblies of most speakers which are rejected in manufacturing test procedure.

It further permits the cleaning of the air gap in case foreign matter has contaminated it during the manufacturing procedure. If the speaker was rejected in test due to a contaminated air gap, the removable magnetic unit provided by this invention would allow the salvage of the complete speaker assembly.

The magnetic unit itself provides a reduction in the cost of making loudspeakers because of its two-piece molded construction. Many speakers require elaborate magnetic structures including top and bottom plates together with additional elements for mounting the magnetic structure on the diaphragm frame.

Since other modifications and changes varied to fit particular operating requirements and environments will be apparent to those skilled in the art, this invention is not considered limited to the examples chosen for purposes of disclosure and covers all modifications and changes which do not constitute departure from the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A loudspeaker comprising: a frame having an end portion thereof, said end portion defining an aperture in the frame having a perimeter including a slotted segment; a diaphragm having a voice coil positioned thereon; said diaphragm mounted on said frame in a manner for disposition of said coil in proximity to said aperture; and a composite magnetic unit mounted on said frame at said aperture, said unit including a unitary cup shaped element of molded magnetic material having a mouth portion thereof, a pole piece of magnetic material mounted within said cup, and an annular element of magnetic material secured to said cup element at said mouth portion, said annular element having a flange portion including a proiection thereon for securing said magnetic unit to said frame and a body portion extending within said cup for providing an inside shoulder for said cup in the vicinity of said mouth Whereby said shoulder and pole piece define a narrow annular air gap therebetween.

2. A loudspeaker comprising: a diaphragm mounting frame having an end portion thereof, said end portion defining an aperture in the frame having a perimeter including a plurality of slotted segments; a diaphragm having a voice coil positioned thereon; said diaphragm mounted on said frame in a manner for disposition of said coil in proximity to said aperture; and a composite magnetic unit mounted on said frame at said aperture; said unit including a unitary cup shaped element of molded magnetic material having a mouth portion thereof and an inner surface defining a cavity of generally circular cross section, a pole piece of magnetic material mounted Within the cavity of said cup, and an annular element of magnetic material secured to said cup element at said mouth portion, said annular element having a flange portion including a tab thereon for securing said magnetic unit to said frame and a body portion extending within said cup and providing an inside shoulder for said cup in the vicinity of said mouth whereby said shoulder and pole piece define a narrow annular air gap therebetween.

3. A permanent magnet unit for establishing a magnetic field for a loudspeaker including a frame having a mounting slot therein, said unit comprising: a unitary cup shaped element of molded magnetic material having a mouth portion thereof, a magnetic pole piece mounted within said cup, and an annular element of magnetic material secured to said cup element at said mouth portion, said annular element including means for removably engaging the slot in the frame for demountably securing said magnetic unit to the frame, said annular element including a body portion extending within said cup and providing an inside shoulder for said cup in the vicinity of said mouth Whereby said shoulder and pole piece define anarrow annular air gap therebetween.

References Cited by the Examiner UNITED STATES PATENTS 1,905,702 4/1933 Hardisty 179-1155 2,025,127 12/1935 Rowe 179-1155 2,551,949 5/1951 Hunter 179-1155 2,590,935 4/ 1952 Charlesworth 179-1155 2,894,182 7/1959 Zuerker et al 179-1155 FOREIGN PATENTS 1,085,191 7/1960 Germany.

ROBERT H. ROSE, Primary Examiner.

WILLIAM C. COOPER, Examiner. 

1. A LOUDSPEAKER COMPRISING: A FRAME HAVING AN END PORTION THEREOF, SAID END PORTION DEFINING AN APERTURE IN THE FRAME HAVING A PERIMETER INCLUDING A SLOTTED SEGMENT; A DIAPHRAGM HAVING A VOICE COIL POSITIONED THEREON; SAID DIAPHRAGM MOUNTED ON SAID FRAME IN A MANNER FOR DISPOSITION OF SAID COIL IN PROXIMITY TO SAID APERTURE; AND A COMPOSITE MAGNETIC UNIT MOUNTED ON SAID FRAME AT SAID APERTURE, SAID UNIT INCLUDING A UNITARY CUP SHAPED ELEMENT OF MOLDED MAGNETIC MATERIAL HAVING A MOUTH PORTION THEREOF, A POLE PIECE OF MAGNETIC MATERIAL MOUNTED WITHIN SAID CUP, AND AN ANNULAR ELEMENT OF MAGNETIC MATERIAL SECURED TO SAID CUP ELEMENT AT SAID MOUTH PORTION, SAID ANNULAR ELEMENT HAVING A FLANGE PORTION INCLUDING A PROJECTION THEREON FOR SECURING SAID MAGNETIC UNIT TO SAID FRAME AND A BODY PORTION EXTENDING WITHIN SAID CUP FOR PROVIDING AN INSIDE SHOULDER FOR SAID CUP IN THE VICINITY OF SAID MOUTH WHEREBY SAID SHOULDER AND POLE PIECE DEFINE A NARROW ANNULAR AIR GAP THEREBWTWEEN. 